The 6th and 9th of August in the year 1945 would change the human race forever. These were the dates on which the United States dropped the first and so far only atomic bomb on an enemy country in wartime. The order to begin nuclear weapons research came from President Franklin Delano Roosevelt. The Manhattan Project did not begin until seven days after Pearl Harbor. The name comes from where the U.S. Army Corps of Engineers were assigned to work in Manhattan's engineering district (Miscamble 8). The test site where most of the testing took place was in Alamogordo, New Mexico. This site was called the Trinity Test Site and was headed by nuclear physicist Robert Oppenheimer (Miscamble 60). There are two types of atomic bombs: fission and fusion. Fusion bombs are also called implosion bombs. Fusion works because it combines two smaller atoms, releasing huge amounts of energy. The disadvantage of fusion is that it is difficult to control. Fission works by splitting a large unstable atom with a particle. This particle hits the nuclei of the atom causing them to break and start a chain reaction. You can control fission by selecting the number of neutrons in the atom (atomicarchive.com). Robert Oppenheimer was born in New York City on April 22, 1904. His father was a German textile merchant and his mother was an artist. From an early age he knew he wanted to be a chemist. He attended Harvard and graduated in 1922. When he was twenty-two, he received his doctorate. while studying with Max Born at the University of Göttingen. Oppenheimer later became a professor at the University of California at Berkley. When World War II began, he was enthusiastically involved in the development of the atom... middle of paper... but the location of the second bomb's dropping was up in the air. The locations of the second bomb were Kokura, Kyoto and Niigata. The bomb detonated over Nagasaki was an implosion device that was tested in the first nuclear detonation at Alamogordo, New Mexico in 1945. Radiochemical research of nuclear fallout and measurements of fireball formation from the test were used to establish the yield of the Nagasaki bomb as twenty kilotons). The Hiroshima bomb was a gun-like device in which two subcritical pieces of enriched uranium were pushed together to create the explosion. The Hiroshima bomb was the only one of its kind ever detonated. The determination of the yield for the Hiroshima explosion depends on theoretical calculations and measurements of the effects of the Hiroshima explosion. The calculated yield for the Hiroshima device is currently 16 ± 2 kt (Chap 2).